How much does it matter which character you choose?

[phrozz]

Seems like each character only has differences in their traits? Still, they all get access to the same cards per their class so I assume resistances would be a more important determining factor? I am new so I am trying to figure out if it's even worth unlocking the rest of the characters right now

[el Darkness]

You can beat the game with starting team, other heroes add more variety in Talents which are working well with different cards depending on hero and have different starting decks which makes building a particular deck easier or harder than other.

In example all Healers will try to make sure that your team will be healthy, but they are doing it in different ways. Reginald is your classic healer who heals wounds with healing spells, while Ottis will not only try to heal your heroes but also prevent further injuries with shield.

[Syrris]

Those talents and individual cards actually make quite a difference in how the characters play over the course of the game. This is somewhat masked by the default party being generalists; the others each lean into specific things and will be much more effective at those things than the generalists will.

[forcecomdr]

As others have said, the talents make a huge difference in how they play. However don't over look party synergy.

For example, Naz heals based on how many stacks of sight and insanity are on mobs, Sylvie has a talent that adds sight to every attack, thereby making heals stronger while doing damage.
Zek adds dark charges with each hit, this works well with the shaman chick for double the boom.
You can mix and match however you want really, but some combos are stronger than others.

[Shneekey]

Each character has their 'shtick', their thing they lean into. This isn't handled by their deck, but by their level upgrades.

For example, Nez passively heals the party at the end of the turn based on the number of Insanity charges and Sight charges that exist. Otis heals for a percentage of the shielding he applies. These are things that will change how a given character approaches a fight. For Nez, it is entirely possible, and even quite powerful, to never have a single 'heal spell' in the entire deck, and still carry healing like a champ through his passive.

The game is very beatable with the initial four characters. The rest give you alternate options which lean to different playstyles.

Party synergy, as previously mentioned, can also be helpful. Previously mentioned was Nez healing based on sight stacks and Sylvie stacking on a ton of Sight stacks. Well, Gustav applies tons and tons of Insanity stacks, and also deals almost exclusively Mental damage, meaning Nez and Gustav also have significant synergy.

Each of the mages have their specialty. Well, okay, the base mage you start with is a generalist, do any elemental flavor fairly well. Fire mage loves fire and burn stacks, shocky mage loves lightning and spark stacks, and rat mage loves curses and applying shadow damage and a broad variety of debuffs. Which one works with your playstyle? That's for you to decide.

Each of the scouts have their specialty. Well, the ranger guy you start with is more generalized, but Thul focuses on melee attacks, poison, and using Stealth as a mechanic. Sylvie is an archer that specializes in lots of shooting ranged attacks and empowering with Sharp. Gustav is a Bard specializing in mental damage song spells that apply insanity, but can also support the party with things like dispels and regen application at need.

For the tanks, again your initial one is a good generalist, capable of offense or defense at need. Heiner is Tanky Boi. If you want a wall of 'no thank you', he's your guy. The berserker is the exact opposite, he's more of a DPS than a Tank, leaning into Rage as a mechanic, and requiring you to handle the bleed stacks that generates. Bree is a Thorn Tank. She can often run around with zero shielding or defense, and still kick your ass because every time you hit her, you take a couple hundred damage back at yourself. Just make sure to max out her resistances so she can take those hits.

So, why do you want to unlock the characters? More options, more ways of playing the game, more playstyles that are viable. They're not better, but they are different.